*{
    margin:0;
    padding:0;
    /* 内减 */
    box-sizing: border-box;
}

.wrapper{
    width: 1200px;
    margin: auto;
}

body{
    background-color: #f3f5f7;
}

li{
    list-style: none;
}

a{
    text-decoration: none;
}

.clearfix::before,
.clearfix::after{
    content: "";
    display: table;
}
 .clearfix::after{
    clear: both;
}